This application relates to a method for making multiple density gaskets.
Gaskets are used to seal various housing interfaces in devices which utilize fluid flow. As an example, a gasket is typically placed between the cylinder head and engine block in an engine to seal between the two, and in particular to seal the areas around the cylinder openings. Such gaskets typically extend outwardly of the cylinder openings to seal the areas around the bolts which connect the cylinder head and engine block. The gasket bears the load from the bolted connection of the housing members, and relies upon that load to provide a seal.
Certain areas of the gasket are subject to higher stress than other areas, and may require a denser gasket material to provide an adequate seal or resist deformation of the engine members. In other areas, however, a less dense gasket material will be sufficient. In a typical gasket application, the areas between the cylinder openings require high stress in order to seal. A denser gasket material may be desired between the cylinder openings than would be required radially outwardly of the cylinder openings. In a gasket with otherwise homogeneous density, a dense material could be used in the high stress areas, but would also be used in areas not subject to high stress. This is undesirable since a designer would like to transfer a majority of the force from the housing connection into limited high-stress areas of the gasket, rather than spreading the force equally over the entire gasket area. Using a denser material selectively at the high-stress area allows such focusing.
It is known to manufacture a composite gasket having a first portion of a first density with a second portion of a higher density. The second portion may be used in an area where it is desired to have additional density. Prior art methods of forming these multiple-density gaskets have been undesirably complex.